Adjustable speed drive system for primary loop recirculation pump

ABSTRACT

An adjustable speed drive system for a primary loop recirculation pump capable of keeping a PLR pump operating even if a single malfunction occurred in a main adjustable speed drive circuit portion. The drive system for the primary loop recirculation pump has a backup main adjustable speed drive circuit portion, and a breaker for switching between an incoming destination and an outputting destination of the backup main adjustable speed drive circuit portion. A control signal of an inverter control portion is switched to control an inverter included in the backup main adjustable speed drive circuit portion, and when a malfunction occurred in the adjustable speed drive main circuit, by switching to the backup main adjustable speed drive circuit portion, the primary loop recirculation pump of a nuclear reactor is continuously controlled and operated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to subject matter described in the patentapplication Ser. No. 11/032,289 (claiming the priority from Japanesepatent application No. 2004-9974 filed on Jan. 19, 2004) filed on Jan.10, 2005, entitled “NUCLEAR POWER PLANT, METHOD OF REPLACEMENT IN THESAME AND METHOD OF OPERATING THE SAME,” by Masashi SUGIYAMA, YukihiroKATAYAMA, Kenji TOMINAGA, Hirohisa SATOMI and Ichirou SHIMODA, andassigned to the same assignee of the present application.

BACKGROUND OF THE INVENTION

The present invention relates to an adjustable speed drive system for aprimary loop recirculation pump for a nuclear reactor coolant, which issuitable for driving and controlling a primary loop recirculation pumpwhich controls power output of a nuclear reactor of a nuclear powerplant.

Conventionally, a flow control of a reactor core has been performed by aprimary loop recirculation pump (a PLR pump) in order to control anuclear reactor power output. In a BWR (stands for Boiling-WaterReactor) plant, the power output control of the nuclear reactor has beenperformed by employing PLR pumps in the two system configuration, and anMG set has been used as its power supply system for variably controllinga rotating speed of a motor which is connected to the primary looprecirculation pump. The MG set is constituted to include an inductionmotor, which is connected to each of two system of high voltage buses inthe plant via an incoming breakers, and rotated by an electric powersupplied from the high voltage bus, a variable-speed fluid couplingconnected to a rotating shaft of the induction motor, and a generatorconnected to the variable-speed fluid coupling. The generator has amotor connected thereto via a breaker for tripping a primary looprecirculation pump (hereinafter referred to as RPT breaker), so that anelectric power generated by the generator is supplied to the motor viathe RPT breaker, and the rotating speed of the generator is controlledby the variable fluid coupling to control electric voltage and frequencysupplied to the motor to thereby control the rotating speed of theprimary loop recirculation pump so as to eventually control the flowamount of the nuclear reactor coolant.

In the conventional technique using the MG set, when a turbine trip or aload rejection occurs during the plant operation, the MG set is usedtogether with the scram of the nuclear reactor to make shutting down ofthe RPT beaker and to trip the two PLR pumps so as to rapidly reduce theflow of the reactor core to thereby moderating a transient increase inpower output from the nuclear reactor, so that sound performance of thefuel is maintained.

In recent years, by virtue of a development of a power semiconductordevice with large capacity, a static variable-frequency power supply (aninverter) using the power semiconductor device, instead of the MG set,came into use. As a result, the conventional MG set has been becomingobsolete, and gradually the static variable-frequency power supply hasbeen instead adopted. JP-A-8-80061 discloses an power supply system fora primary loop recirculation pump adopting a current source inverter.

Compared to the primary loop recirculation pump using the MG set, apower generation plant adopting the inverter power supply system doesnot require the MG set which consists of an induction motor, avariable-speed fluid coupling, a generator, and an oil system as anauxiliary machinery, therefore, there are some advantages such asenhancement of maintainability, effectiveness during low power output,and linearity of speed control, and the like.

SUMMARY OF THE INVENTION

In the power supply system for the primary loop recirculation pump forthe nuclear reactor coolant adopting the current source inverterdisclosed in JP-A-8-80061, the current source inverter serves as acurrent source on an electric circuit, it is not possible to performno-load operation by shutting down the output side of the inverter.Therefore, when a trouble such as turbine trip or load rejection occursin a plant, it has been first tripping an inverter incoming breakerprovided between the system and the current source inverter by using anRPT signal from a recirculation pump trip control portion (hereinafterreferred to as a RPT control portion), and then stopping the currentsource inverter by using a stop signal from the inverter control portionin order to stop two PLR pumps.

Furthermore, with the PLR pump, two PLR pumps constituted into twoseparate systems are employed for performing controlling of the poweroutput of the nuclear reactor. Therefore, in the case that one of thetwo systems comes into malfunction due to breakage of one of the PLRpumps, generation of the power output from the nuclear plant must belowered, hence high reliability is required in the power supply of theprimary loop recirculation pump. Therefore, the inverter control portionis usually designed to have a redundancy so as not to stop the plant byonly one malfunction of the inverter portion. However, a main power gatesupply circuit portion which supplies electric power to the PLR pumpmotors, by including an inverter or an inverter driver for supplying agate pulse to the inverter, and the like, is formed in a one-fold (i.e.,single) configuration.

Since a semiconductor element used for an inverter main circuit, a gatedriver, and the like, may lose its function by an accidentalmalfunction, there is a possibility that one accident leads theadjustable speed drive main circuit portion to be inoperable.

Therefore, it is an object of the present invention to provide anadjustable speed drive for a primary loop recirculation pump which isable to continue the operation of a PLR pump even if a singlemalfunction occurred in an adjustable speed drive main circuit portion.

It is another object of the present invention to provide an adjustablespeed drive for a primary loop recirculation pump which is able to tripa PLR pump rapidly and safely, and to continue the operation of the PLRpump even if a single malfunction or failure occurred in the adjustablespeed drive main circuit portion.

To achieve the above objectives, the adjustable speed drive for theprimary loop recirculation pump according to the present invention is anadjustable speed drive for a primary loop recirculation pump using aninverter, which includes a backup main adjustable speed drive circuitportion, and a breaker for switching between an incoming destination andan outputting destination of the backup main adjustable speed drivecircuit portion. A control signal of an inverter control portion isswitched in order to control an inverter included in the backup mainadjustable speed drive circuit portion, and thus, even if a singlemalfunction occurred in the adjustable speed drive main circuit, theprimary loop recirculation pump of a nuclear reactor is continuouslycontrolled and operated by switching to the backup main adjustable speeddrive circuit portion. Thereby, even if a single malfunction occurred inthe main adjustable speed drive portion, it is possible to provide ahighly reliable adjustable speed drive for a primary loop recirculationpump.

According to an embodiment of the present invention, the adjustablespeed drive for the primary loop recirculation pump includes a backupmain adjustable speed drive circuit portion, and a breaker for switchingbetween an incoming destination and an outputting destination of thebackup main adjustable speed drive circuit portion, and in order tocontrol an inverter included in the backup adjustable speed drive maincircuit portion, a control signal of an inverter control portion isswitched. Thus, when a single malfunction occurs in a main adjustablespeed drive circuit, switching to the backup adjustable speed drive maincircuit portion is performed, the primary loop recirculation pump of anuclear reactor can be continuously controlled and operated.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general diagrammatic view showing a configuration of aadjustable speed drive for the primary loop recirculation pump accordingto an embodiment of the preset invention.

FIG. 2 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment shown in FIG. 1.

FIG. 3 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment shown in FIG. 2.

FIG. 4 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment of FIG. 2.

FIG. 5 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment shown in FIG. 1.

FIG. 6 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment shown in FIG. 2.

FIG. 7 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment shown in FIG. 6.

FIG. 8 is a general diagrammatic view illustrating a modified embodimentof the configuration of the adjustable speed drive for the primary looprecirculation pump according to the embodiment shown in FIG. 6.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described hereinbelowwith reference to FIGS. 1 through 8.

FIG. 1 is a general diagrammatic view illustrating a configuration of anadjustable speed drive for a primary loop recirculation pump accordingto the embodiment of the present invention.

As shown in FIG. 1, a transformer 7 is connected to a high voltage bus 1of unit auxiliary power supply system via a breaker 3, and a transformer9 is connected to a high voltage bus 2 via a breaker 6, in a plant.Furthermore, a breaker 4 is connected to the high voltage bus 1, abreaker 5 is connected to the high voltage bus 2, and a transformer 8 isconnected to the breaker 4 and the breaker 5. An inverter 10 isconnected to the transformer 7, a backup inverter 11 is connected to thetransformer 8, and an inverter 12 is connected to the transformer 9. Theinverter 10 is connected to an RPT breaker 17 via a breaker 13, and thebackup inverter 11 is connected to the RPT breaker 17 via a breaker 14.The RPT breaker 17 is connected to a PLR pump 21 via a PLR pump motor19. The backup inverter 11 is connected to a RPT breaker 18 via abreaker 15, and the inverter 12 is connected to the RPT breaker 18 via abreaker 16. The RPT breaker 18 is connected to a PLR pump 22 via a PLRpump motor 20. The PLR pumps 21 and 22 are connected to a nuclearreactor 40 via a primary loop piping 36, and a flow of nuclear reactorcoolant in the reactor core of a nuclear reactor 40 is controlled byboth the PLR pump 21 and the PLR pump 22.

A nuclear reactor recirculation control portion 23 is connected to aninverter control portion 25 and an inverter control portion 26. Theinverter control portion 25 is connected to the inverter 10 via aninterface 30 and a gate driver 31, and the inverter control portion 26is connected to the backup inverter 11 via an interface 32 and a gatedriver 33. The gate driver 31 is driven by a signal from the invertercontrol portion 25 to supply a gate pulse to the inverter 10.

A nuclear reactor recirculation control portion 24 is connected to theinverter control portion 26 and an inverter control portion 27. Theinverter control portion 27 is connected to the inverter 12 via aninterface 34 and a gate driver 35. The gate driver 35 is driven by asignal from the inverter control portion 27 to supply a gate pulse tothe inverter 12.

A malfunction detection portion 28 is provided to monitor an operationstate of the adjustable speed drive for the primary loop recirculationpump for detecting malfunctions that might occur in the adjustable speeddrive. Although not illustrated in FIG. 1, a further malfunctiondetection portion is provided for an inverter 12, to monitor a state ofthe operation of the adjustable speed drive system for the primary looprecirculation pump for detecting malfunctions.

In this way, a two-system primary loop recirculation system isconfigured of the PLR pump 21 and the PLR pump 22. In the normaloperation, the breaker 3, the breaker 13 and the RPT breaker 17 areclosed to supply electric power from the inverter 10 to the PLR pumpmotor 19, and further the breaker 6, the breaker 16 and the RPT breaker18 are closed to supply electric power from the inverter 12 to the RPTpump motor 20. In this instance, the breaker 4 or the breaker 5 isarranged to be closed, and the breaker 14 and the breaker 15 arearranged to be opened and accordingly, any supply of an electric powerto the PLR pump motor 19 or the PLR pump motor 20 is not performed.However, the backup inverter 11 is electrically charged and in a standbystate. In this instance, if both the breaker 4 and the breaker 5, orboth the breaker 14 and the breaker 15 are turned to be simultaneouslyclosed, electric power is supplied to either the PLR pump motor 19 orthe PLR pump motor 20 from both the backup inverter 11 and the inverter10, or the inverter 12. Therefore, an interlock is provided to avoid theboth breakers from turning to be closed at the same time. Also, theinverter control portion 26 of the backup inverter 11 is in standby in astate in which the inverter control portion 26 is able to follow thecontrol signal from either the nuclear reactor recirculation controlportion 23 or 24.

In this situation, for example, when the malfunction detection portion28 detects malfunction in the adjustable speed drive main circuitportion for supplying electric power to the PLR pump motor, which isprovided with the inverter 10 for supplying electric power to the PLRpump motor 19, the gate driver 31 for supplying a gate pulse to theinvert 10, the inverter control portion 25, and the like, the breaker 3and the breaker 13 are shut down to be opened, and also the inverter 10is stopped and the breaker 14 is put into its closed state to therebydrive the backup inverter 11, which is in a standby state. Therefore,the inverter for supplying electric power to the PLR pump motor 19 isswitched to the backup inverter 11, and the operation of the PLR pumpmotor 19 is continued.

Upon switching to the backup inverter 11, the breaker 5 is closed, andwhen electric power is supplied to the backup inverter 11 also from thehigh voltage bus 2, the high voltage bus 2 also supplies electric powerto the inverter 12. In this case, after the inverter is switched to thebackup inverter 11 and after the entire operation is stabilized, thebreaker 4 is closed, subsequently the breaker 5 is opened, and then thehigh voltage bus 2 is switched to the high voltage bus 1 so as toachieve supply of the electric power from the high voltage bus 1.Furthermore, if the inverter control portion 26 of the backup inverter11 is able to follow the control signal from the nuclear reactorrecirculation control portion 24 during the standby state thereof, whenthe operation has been stabilized, the inverter control portion 26 willbe switched to control the backup inverter 11 according to the controlsignal from the nuclear reactor recirculation control portion 23.

Furthermore, if a malfunction or failure occurs in the adjustable speeddrive main circuit portion for the inverter 12 supplying electric powerto the PLR pump motor 20, the malfunction detection portion detects themalfunction, and the breaker 6 and the breaker 16 are shut down to beopened. Then, the inverter 20 is stopped, the backup inverter 11 isactivated, and the breaker 15 is turned to be closed, so that theadjustable speed drive main circuit portion causing the malfunction isswitched to the backup adjustable speed drive main circuit portion to beable to continue the operation of the PLR pump motor 20. Furthermore,like the case described above, if the breaker 4 is closed, and electricpower is supplied from the high voltage bus 1 to the backup inverter 11,after the inverter is switched to the backup inverter 11 and theoperation is stabilized, the breaker 5 is closed, subsequently thebreaker 4 is shut down to be switched to its opened state. Furthermore,if the inverter control portion 26 of the backup inverter 11 is able tofollow the control signal from the nuclear reactor recirculation controlportion 23 during the standby state of the inverter control portion 26,after the operation is stabilized, the inverter control portion 26 willbe switched to control the backup inverter 11 according to the controlsignal from the nuclear reactor recirculation control portion 24.

A voltage source inverter is adapted for the inverter 10, 11 and 12,they are operated with a fixed voltage/frequency based on an invertercontrol signal from the inverter control portion so that the rotatingspeed of the PLR pump motor is controlled. In this instance, since thevoltage source inverter is used, even if a turbine trip or a loadrejection occurred, it is possible to deal with such trip or loadrejection by shutting down the PRT breaker in the output side of theinverter. Therefore, the PLR pump motor can be tripped rapidly andsafely by the stopping of the operation of the voltage source inverter.

FIG. 2 is a view showing a modified embodiment from the embodiment asshown in FIG. 1. The embodiment shown in FIG. 2 has a configurationsimilar to the embodiment shown in FIG. 1, however, an inverter controlportions 50, 51, and 52 of the embodiment of FIG. 2 have a two-fold(i.e., dual) configuration. That is to say, each of the inverter controlportions 50, 51, and 52 has two control portions, and each of thecontrol portions are connected to the nuclear reactor recirculationcontrol portion 23 and 24 respectively. By using this configuration,when a malfunction occurred in the control portion of the invertercontrol portions 50, 51, and 52 during the operation, it is possible toswitch to a standby control portion of the inverter control portions 50,51 and 52. Therefore, when a malfunction of any inverter control portionoccurred, it is possible to take a measure of switching of controlportion.

When a malfunction occurred in the adjustable speed drive main circuitportion, the adjustable speed drive main circuit portion is switched tothe backup in a manner similar to the embodiment of FIG. 1, and thus theoperation of the PLR pump motor can be continued.

FIG. 3 is a general view showing a modified embodiment from theembodiment shown in FIG. 2. In the embodiment shown in FIG. 3, insteadof the backup inverter control portion 51 of the embodiment of FIG. 2,inverter control signal switches 53, 54, 55 and 56 are provided. Eachcontrol portion between an interface 30 and the two control portions ofan inverter control portion 50 has a branch portion, and each of thebranch portions are connected to a terminal of an inverter controlsignal switch 53 and a terminal of an inverter control signal switch 54respectively. Further, each connection portion between an interface 34and two control portions of an inverter control portion 52 has a branchportion, and each of the branch portions are connected to a terminal ofan inverter control signal switch 55 and a terminal of an invertercontrol signal switch 56 respectively. The other terminal of theinverter control signal switch 53 and the other terminal of the invertercontrol signal switch 54 are connected to the interface 32 respectively.Further, a malfunction detection portion 28 is connected to the invertercontrol signal switch 53 and 54. When the inverter control signal switch53 or the inverter control signal switch 54 is turned “on”, amalfunction in a backup inverter 11 or a gate driver 33 can be detectedvia an interface 32.

In this embodiment, when if there is a malfunction in any of theinverter 10, the gate driver 31 or the interface 30, the malfunctiondetection portion 28 detects the malfunction, a breaker 13 is shut downto be opened, and a breaker 14 is put into its closed state.Subsequently, the inverter control signal switch for a control portionused by the inverter control portion 50 is turned “on” and theconnection destination of the inverter control portion 50 is switched tothe backup inverter 11 to continue controlling the PLR pump motor 19 byusing the backup inverter 11. In this instance, an interlock is providedto the inverter control signal switch 53, 54, 55 and 56 to avoid theyare turned to be closed at the same time.

By using this configuration, when a malfunction occurred in theadjustable speed drive main circuit portion, the backup inverter 11 canbe controlled by making use of the inverter control portion in which themalfunction occurred, and thus the control and the operation of the PLRpump motor can be continued.

FIG. 4 is a general view showing a modified embodiment from theembodiment shown in FIG. 2. The embodiment shown in FIG. 4 has aconfiguration similar to the embodiment shown in FIG. 2, however, aone-fold or single inverter control portion 26 is used for an invertercontrol portion of a backup inverter 11 in FIG. 4.

FIG. 5 is a general view showing a modified embodiment of the embodimentshown in FIG. 1. An embodiment shown in FIG. 5 has a configurationsimilar to the example shown in FIG. 1. However, in the embodiment inFIG. 1, the high voltage buses 1 and 2 are connected via the breaker 4and 5 to the shared transformer 8, but in FIG. 5, a high voltage bus 1is connected to a transformer 8 a via a breaker 4, and a high voltagebus 2 is connected to a transformer 8 b via a breaker 5, so that abackup inverter 11 and an inverter control portion 26 are provided foreach system.

That is, the high voltage bus 1 is connected to the transformer 8 a viathe breaker 4, and a backup inverter 11 a, the breaker 14 and an RPTbreaker 17 are connected to the transformer 8 a in series. From anuclear reactor recirculation control portion 23, an inverter controlportion 26 a, an interface 32 a and a gate driver 33 a are sequentiallyconnected to the backup inverter 11 a.

On the other hand, the transformer 8 b is connected to the high voltagebus 2 via the breaker 5, and a backup inverter 11 b, the breaker 15 andan RPT breaker 18 are connected to the transformer 8 b in series. Fromthe nuclear reactor recirculation control portion 24, an invertercontrol portion 26 b, an interface 32 b and a gate driver 33 b aresequentially connected to the backup inverter 11 b.

In the normal operation, a breaker 3 and a breaker 13 in the system ofthe high voltage bus 1 are closed, and electric power is supplied froman inverter 10 to a PLR pump motor 19. In this instance, the breaker 4is closed, the breaker 14 is opened, the backup inverter 11 a is in astandby state while being electrically charged, and an inverter controlportion 26 a is in a standby state following a signal from the nuclearreactor recirculation control portion 23. A breaker 6 and a breaker 16in the system of the high voltage bus 2 are closed, and electric poweris supplied from an inverter 12 to a PLR pump motor 20. In thisinstance, the breaker 5 is closed, the breaker 15 is opened, the backupinverter 11 b is in a standby state while being electrically charged,and an inverter control portion 26 b is in a standby state following asignal from the nuclear reactor recirculation control portion 24.

In this instance, for example, if a malfunction occurred in anadjustable speed drive circuit portion for supplying electric power to aPLR pump 21 which is in the high voltage bus 1 side, a malfunctiondetection portion 28 detects the malfunction, and the breaker 3 and thebreaker 13 are shut down to be opened. Then, the inverter 10 is stopped,the backup inverter 11 a is activated, and the breaker 14 is turned tobe closed, so that the adjustable speed drive main circuit portion inthe high voltage bus 1 side is switched to the backup to be able tocontinue the operation of the PLR pump motor 19.

Thus, since the backup inverter control portion and the adjustable speeddrive main circuit portion are provided for each system of the highvoltage bus, there is an advantage that switching control to the backupis facilitated.

FIG. 6 is a general view showing a modified embodiment from theembodiment shown in FIG. 2. An embodiment shown in FIG. 6 has aconfiguration similar to the embodiment shown in FIG. 2. However, in theembodiment of FIG. 2, the high voltage buses 1 and 2 are connected viathe breakers 4 and 5 to the shared transformer 8, but in FIG. 6, a highvoltage bus 1 is connected to a transformer 8 a via a breaker 4, and ahigh voltage bus 2 is connected to a transformer 8 b via a breaker 5, sothat a backup inverter 11 and an inverter control portion 51 areprovided for each system.

That is, the high voltage bus 1 is connected to the transformer 8 a viathe breaker 4, and a backup inverter 11 a, the breaker 14 and an RPTbreaker 17 are connected to the transformer 8 a in series. From anuclear reactor recirculation control portion 23, an inverter controlportion 51 a, an interface 32 a and a gate driver 33 a are sequentiallyconnected to the backup inverter 11 a.

On the other hand, the transformer 8 b is connected to the high voltagebus 2 via the breaker 5, and a backup inverter 11 b, the breaker 15 andan RPT breaker 18 are connected to the transformer 8 b in series. Fromthe nuclear reactor recirculation control portion 24, an invertercontrol portion 51 b, an interface 32 b and a gate driver 33 b aresequentially connected to the backup inverter 11 b.

In the normal operation, a breaker 3 and a breaker 13 in the system ofthe high voltage bus 1 are closed, and electric power is supplied froman inverter 10 to a PLR pump motor 19. In this instance, the breaker 4is closed, the breaker 14 is opened, the backup inverter 11 a is in astandby state while being electrically charged, and an inverter controlportion 51 a is in a standby state following a signal from the nuclearreactor recirculation control portion 23. A breaker 6 and a breaker 16in the system of the high voltage bus 2 are closed, and electric poweris supplied from an inverter 12 to a PLR pump motor 20. In thisinstance, the breaker 5 is closed, the breaker 15 is open, the backupinverter 11 b is in a standby state while being charged, and an invertercontrol portion 51 b is in a standby state following a signal from thenuclear reactor recirculation control portion 24.

In this instance, for example, if a malfunction occurred in anadjustable speed drive main circuit portion for supplying electric powerto a PLR pump 21 which is in the high voltage bus 1 side, a malfunctiondetection portion 28 detects the malfunction, and the breaker 3 and thebreaker 13 are shut down to be opened. Then, the inverter 10 is stopped,the backup inverter 11 a is activated, and the breaker 14 is turned tobe closed, so that the adjustable speed drive main circuit portion inthe high voltage bus 1 side is switched to the backup system so as to beable to continue the operation of the PLR pump motor 19.

Thus, since the backup inverter control portion and the adjustable speeddrive main circuit portion are provided for each system of the highvoltage bus, there is an advantage that switching control to the backupsystem is facilitated.

FIG. 7 is a general view showing a modified embodiment from theembodiment shown in FIG. 6. The embodiment shown in FIG. 7 has aconfiguration similar to the embodiment shown in FIG. 6, however, abackup inverter control portion is omitted in the embodiment of FIG. 7.That is, each signal line which branches from each of connectionportions between an interface 30 and two control portions of an invertercontrol portions 50 is connected to an interface 32 a, and the invertercontrol portion 51 a (FIG. 6) is omitted. Furthermore, each signal linewhich branches from each of connection portions between an interface 34and two control portions of an inverter control portions 52 is connectedto an interface 32 b, and the inverter control portion 51 b (FIG. 6) isomitted.

By using this configuration, if a malfunction occurred in the adjustablespeed drive main circuit portion, the connection between the invertercontrol portion and the interface is switched to a backup side, and thusthe control and the operation of the PLR pump motor can be continued.

FIG. 8 is a general view showing a modified embodiment from theembodiment shown in FIG. 6. The embodiment shown in FIG. 8 has aconfiguration similar to the embodiment shown in FIG. 6, however, abackup inverter control portion is a one-fold inverter control portion26 in FIG. 8.

According to the embodiment of the present invention, the adjustablespeed drive for the primary loop recirculation pump includes a backupadjustable speed drive main circuit portion, and a breaker for switchingbetween an incoming destination and an outputting destination of thebackup adjustable speed drive main circuit portion. A control signal ofan inverter control portion is switched in order to control an inverterthat is a constituent of the backup adjustable speed drive main circuitportion, and thus, even if a malfunction occurred in the adjustablespeed drive main circuit, the primary loop recirculation pump of anuclear reactor is continuously controlled and operated by switching tothe backup adjustable speed drive main circuit portion.

Furthermore, since the backup adjustable speed drive is provided, if amalfunction occurred in the control portion, by performing switching ofthe adjustable speed drive main circuit control portion, even if thecontrol portion is the one-fold configuration, it is possible to providean adjustable speed drive for a primary loop recirculation pump which ishighly reliable, has a redundancy, and of which cost and install spaceare reduced.

Furthermore, by controlling the backup inverter by using the controlportion of the adjustable speed drive main circuit portion in which amalfunction occurred, it is not required to provide a backup invertercontrol portion, therefore it is possible to provide an adjustable speeddrive for a primary loop recirculation pump of which cost andinstallation space are reduced.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. An adjustable speed drive system for a primary loop recirculation pump, comprising: two adjustable speed drive systems, each being provided with a first breaker connected to a high voltage bus of unit auxiliary power supply system, an inverter connected to the first breaker via a transformer, a second breaker connected to an output side of the inverter, a gate driver that supplies a gate pulse to the inverter, and an inverter control portion that drives the gate driver; and a backup adjustable speed drive system, wherein when a malfunction detection portion detects a malfunction in a main adjustable speed drive circuit portion including the inverter and the gate driver in one of the two adjustable speed drive systems, the main adjustable speed drive circuit portion is switched to a backup adjustable speed drive system, and an operation of a recirculation pump motor for driving a recirculation pump that controls a flow of a reactor core is continued.
 2. The adjustable speed drive system for the primary loop recirculation pump according to claim 1, wherein one system of the backup adjustable speed drive system is provided, and wherein both the inverter control portion of the backup adjustable speed drive system and the inverter control portions of the two adjustable speed drive systems are configured by one control portion.
 3. The adjustable speed drive system for the primary loop recirculation pump according to claim 1, wherein one system of the backup adjustable speed drive system is provided and wherein both the inverter control portion of the backup adjustable speed drive system and the inverter control portions of the two adjustable speed drive systems are configured by two control portions.
 4. The adjustable speed drive system for the primary loop recirculation pump according to claim 1, wherein one system of the backup adjustable speed drive system is provided, and each inverter control portion of the two adjustable speed drive systems is configured by two control portions, and wherein the two control portions are connected to the inverter of the backup adjustable speed drive system.
 5. The adjustable speed drive system for the primary loop recirculation pump according to claim 1, wherein the inverter control portions of the two adjustable speed drive systems are two-folded or dual configuration, and the inverter portion of the backup adjustable speed drive system is one-folded or single configuration.
 6. An adjustable speed drive system for a primary loop recirculation pump, comprising: an adjustable speed drive system provided with a first breaker connected to a high voltage bus of unit auxiliary power supply system, an inverter connected to the first breaker via a transformer, a second breaker connected to an output side of the inverter, a gate driver that supplies a gate pulse to the inverter, and an inverter control portion that drives the gate driver; the adjustable speed drive system being combined with a system of a backup adjustable speed drive system to form a set of adjustable speed drive systems, said adjustable speed drive for a primary loop recirculation pump having the two sets of adjustable speed drive systems, wherein when a malfunction detection portion detects a malfunction in a main adjustable speed drive circuit portion including the inverter and the gate driver in one of the two adjustable speed drive sets used in a normal operation, the main adjustable speed drive circuit portion is switched to one of the backup adjustable speed drive systems and an operation of a recirculation pump motor for driving a recirculation pump that controls a flow of a reactor core is continued.
 7. The adjustable speed drive system for the primary loop recirculation pump according to claim 6, wherein each inverter control portion of the two adjustable speed drive sets is configured by one control portion.
 8. The adjustable speed drive system for the primary loop recirculation pump according to claim 6, wherein each inverter control portion of the two adjustable speed drive sets are configured by two control portions.
 9. The adjustable speed drive system for a primary loop recirculation pump according to claim 6, wherein the inverter control portions of one of the two adjustable speed drive systems is two-folded or dual configuration, and the inverter portion of the backup adjustable speed system is one-folded or single configuration.
 10. An adjustable speed drive system for a primary loop recirculation pump, comprising two adjustable speed drive sets which are arranged in parallel, each of the two adjustable speed drive sets including an adjustable speed drive system and a backup adjustable speed drive system, wherein the adjustable speed drive system includes a first breaker connected to a high voltage bus of unit auxiliary power supply system, an inverter connected to the first breaker via a transformer, a second breaker connected to an output side of the inverter, a gate driver that supplies a gate pulse to the inverter, and an inverter control portion having two control portions that drive the gate driver, wherein the backup adjustable speed drive system includes a first breaker connected to a high voltage bus of unit auxiliary power supply system, an inverter connected to the first breaker via a transformer, a second breaker connected to an output side of the inverter, a gate driver for supplying a gate pulse to the inverter, and wherein the two control portions are connected to the gate driver of the backup adjustable speed drive system via an inverter control signal switch. 